Having killed a bunch of deer with both calibers I can assure you that there is almost no difference in the killing power of the 308 and 30-06. This would hold even more true on any shots under 300 yards. With deer weight bullets 150-180 gr the velocity is so close that the difference would be impossible to see. With bullets heavier than 180 grains and ranges past 300 yards then the 30-06 will outstep the 308. Even then though the difference with a good hit by both rifles would make no practicle difference. I shot 40 deer or so with the 308 and never had one go more than a few yards. Twenty or so with the 30-06 gave the same results. With good shot placement and a good bullets all of the 300 Mags, the 30-06 and the 308 will yield exactly the same results out to 300 yards or so. A dead deer. or elk or moose.